This invention relates to glazing and in particular a system for attaching such glazing to a window frame or mullion.
Various arrangements are known or have been proposed for mounting and supporting single layer glass plates or lights or double layer sealed units in a framework or mullion without exterior stops or caps. Mounting windows in this manner is sometimes known as "flush" glazing. The interior light of a sealed unit or the single sheet of glass can be adhered to the mullion frame in situ or, alternatively, the glass can be adhered to a framework in a factory and then the total combination can be clipped or bolted in place.
In one known method of attachment, the glass light is attached to a metal frame by means of a structural silicone strip and an adjacent compatible tape strip that may be sticky on both sides. The frame has an elongate channel-shaped slot extending along an outwardly facing side thereof, which slot is capable of receiving the end portions of a number of clips that can be used to attach the frame to a main frame or mullion.
Another method for attaching glass plates or sealed glass units to a window frame is that employing a glazing gasket having a H-shaped cross section. Such glazing gaskets are sold by Standard Products Company in the United States. These gaskets which are made from Neoprene sold by Dupont have a separate locking strip that is ten points harder in durometer (shore A) than the gasket itself. The gasket can have a toothed or ribbed extension on one side for attaching the glazing to a window frame. Adjacent edges of two glass sheets or glass units are inserted into the two main cavities of the gasket. In order to attain the sealing pressures which are required to secure and seal the glass panels to the frames, the locking strip is inserted progressively with a special tool into a groove that extends along the length of the gasket.
Other methods for attaching sealed glass units to a window frame are disclosed in applicant's U.S. Pat. No. 4,500,572 issued Feb. 19, 1985. In the system of this patent, the spacers which separate and join the two glass plates are adapted for connection of the unit to adjoining frame members. The spacer has sections forming a channel shaped recess, open along the edge of the unit. Connectors or clips can be used to attach the spacer member to the frame. Alternatively, the spacer can have an extension that extends beyond the edge of the glass unit, which extension is attached by means of screws or clamping plates or both to the mullion frame.
One of the major problems arising from currently used structural silicone glazing or flush glazing is that silicone is difficult to adhere to aluminum or steel. Moisture can penetrate the silicone and slowly cause oxidation of the metal surface and this will eventually affect adhesion. In order to prevent oxidation, the metal surface must generally be treated. In this case of aluminum, the metal is either anodized or painted. Anodizing produces an even oxidized surface which can produce a good surface for adhesion. However, often microscopic surface irregularities contain contaminants which will affect adhesion. Although paint finishes can also produce good adhesion surfaces, commercial formulations are constantly changing, resulting in an alteration in adhesion characteristics. Further, the adhesion of the paint itself must carry the loads on the window and, if the paint is poorly applied, it can peel off.
Another difficulty with current structural silicone glazing is that any small traces of oil from the manufacturing and fabrication process can destroy the adhesion of this material. Accordingly, the surface must be very carefully cleaned prior to application of the silicone and this is not always successful. The most commonly used silicone (acetoxy curing type) also requires that a primer or adhesion promoter be applied to the metal. This operation is difficult as a very thin layer of clean primer must be deposited on the metal surface. In fact, too much primer is almost worse than too little for this purpose. Unlike metal, a glass surface does not need a primer for silicone to adhere to it.
Recent U.S. Pat. No. 4,567,710 issued Feb. 4, 1986 to Michael R. Reed teaches a method of adhering plastic face sheets to a metal I-beam grid core, by the use of plastic connectors. The purpose of the plastic connectors is to improve the thermal insulation of the sandwich panel and to reduce the stresses on the adhesive bond by closely matching the thermal expansion of the face sheets and the connector. The connector material is described as preferably a rigid polyester resin formulation as used in the Fiberglas face sheets. The connectors are fixed to the metal I-beam core by sliding fit. The adhesive stresses in sandwich panels of this nature are almost all produced by differential thermal expansion. On the other hand glass units incorporating the present invention are suitable for large flush glazed glass lites which are typically fixed on high-rise buildings. Under these circumstances, the majority of the adhesive stresses at the perimeter of the glass unit are produced by wind loads and building mvoements, not differential thermal expansion.
It is an object of this invention to provide an improved glass panel unit for use on a building exterior wherein the glass light or panel member is attached to an adjoining frame by means of an elongate elastomeric gasket and wherein this gasket is reliably and securely fastened to the frame.
It is another object of the present invention to provide an improved glass unit that can be used for flush glazing and that provides an effective and reliable means for attaching the glass light to the adjoining frame.
It is a further object of the present invention to provide an improved panel unit for use on a building exterior wherein the panel member is attached to an adjoining frame by means of a flexible gasket and wherein the structural gasket is reliably and securely fastened to the frame.